視覚解剖学 Visual Anatomy

　腋窩神経とは

　以下は「 日本人体解剖学 (上巻) 」の解説文となる。

「 知覚性および運動性。 第5、第6頚神経から起こり、後神経束の枝で肩甲下筋の停止腱の前面を走り、その下縁で後上腕回旋動・静脈とともに大・小円筋の間すなわち外側腋窩隙を通って上腕骨外科頚の後方から三角筋の内面に達し、次の２枝に分かれる。 」

　以下は腕神経叢の後神経束の神経の簡単な図となる。後神経束はそのまま橈骨神経となるが、神経幹からは3つの枝が出ている。　　

　また、以下は腕神経叢を鎖骨上部、鎖骨下部と分けた場合の、鎖骨下部の簡単な図となる。

　以下は「 Wikipedia 」の解説文となる。

「　The axillary nerve or the circumflex nerve is a nerve of the human body, that originates from the brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibers from C5 and C6. The axillary nerve travels through the quadrangular space with the posterior circumflex humeral artery and vein.

　The nerve lies at first behind the axillary artery, and in front of the subscapularis, and passes downward to the lower border of that muscle.
It then winds backward, in company with the posterior humeral circumflex artery, through a quadrangular space bounded above by the teres minor, below by the teres major, medially by the long head of the triceps brachii, and laterally by the surgical neck of the humerus, and divides into an anterior, a posterior, and a collateral branch to the long head of the triceps brachii branch.

• 　The anterior branch (upper branch) winds around the surgical neck of the humerus, beneath the deltoid muscle, with the posterior humeral circumflex vessels. It continues as far as the anterior border of the deltoid to provide motor innervation. The anterior branch also gives off a few small cutaneous branches, which pierce the muscle and supply in the overlaying skin.
• 　The posterior branch (lower branch) supplies the teres minor and the posterior part of the deltoid. The posterior branch pierces the deep fascia and continues as the superior (or upper) lateral cutaneous nerve of arm, which sweeps around the posterior border of the deltoid and supplies the skin over the lower two-thirds of the posterior part of this muscle, as well as that covering the long head of the triceps brachii.
• 　The motor branch of the long head of the triceps brachii arises, on average, a distance of 6 mm (range 2–12 mm) from the terminal division of the posterior cord termination.[1]
• The trunk of the axillary nerve gives off an articular filament which enters the shoulder joint below the subscapularis.

　Variation
Traditionally, the axillary nerve is thought to only supply the deltoid and teres minor. However, several studies on cadaverspointed out that the long head of triceps brachii is innervated by a branch of the axillary nerve.[2][1][3]

　The axillary nerve supplies two muscles in the arm: deltoid (a muscle of the shoulder), and teres minor(one of the rotator cuff muscles).
The axillary nerve also carries sensory information from the shoulder joint, as well as the skin covering the inferior region of the deltoid muscle - the "regimental badge" area (which is innervated by the superior lateral cutaneous nerve branch of the axillary nerve).
The posterior cord of the brachial plexus splits inferiorly to the glenohumeral joint giving rise to the axillary nerve which wraps around the surgical neck of the humerus, and the radial nerve which wraps around the humerus anteriorly and descends along its lateral border.　」

【 語 句 】

・quadrangular space ： 外側腋窩隙　　・ posterior circumflex humeral artery ： 後上腕回旋動脈　　・ subscapularis ： 肩甲下筋　　・ surgical nec k： 外科頚　　・ pierce ： 貫通する　　・ sweep ： ？　　・ glenohumeral joint ： 肩甲上腕関節

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